The application generally relates to electrical power transmission networks. The application relates more specifically to power transmission networks, also referred to hereinafter as the grid, with communication enabled power sources for fast response to a load imbalance or generation imbalance on the grid.
Power transmission systems require reserve power sources to maintain system stability and to respond rapidly to large power imbalances such as loss of a power generating unit or a sudden disconnection of load. Traditionally, system frequency is a parameter that is sensed on a power transmission network or grid, to indicate when it may be necessary to switch contingent power reserves onto the grid, e.g., in response to a loss of generation capacity. With increasing penetration of renewable energy systems, and the corresponding reduction in system inertia, the rate of frequency fluctuation has been increasing after an event. As this trend continues, power systems may be unable to successfully recover from a large generator failure or loss of significant electrical load.
Traditionally, the frequency response of a power system is determined by the combined effort provided by the governing action of individual generators. Control is driven by a feedback signal that adjusts the machine power output level based on local frequency measurements. The governor actuation is typically slow as it involves the movement of synchronous rotating machines that have large inertias. Contrary to these slow acting dynamics of synchronous generation, converter interfaced generators, or CIGs, e.g., photovoltaics (PVs) or energy storage systems, can be applied almost instantaneously to adjust power levels.
Alternate power resources, e.g., energy storage, PV generation, wind generation, and demand response are becoming more prevalent. Currently, methods of sensing frequency of the power transmission grid to maintain sufficient power generation capacity are inadequate to manage alternate reserve power sources. There is a need to control such alternate resources as fast responding imbalance reserve with improved responsiveness over the traditional approach of sensing system frequency drops.
What is needed is a system and/or method for using a communication signal that provides feed-forward control of dispatchable alternate power sources, where a communications network may be employed to quickly inform dispatchable resources that an imbalance has occurred. Dispatchable power sources refers to resources of electricity that can be dispatched at the request of power grid operators or plants, e.g., power generating plants that can be switched on or off of the grid, or may adjust power output accordingly to a predetermined order. Due to their fast-acting grid interfaces, these resources can respond in significantly less time than feedback controlled conventional generators which need to wait until a change in the grid frequency is detected. Such a communication signal may reduce power system fluctuations and instability, and mitigate the impact of power imbalances, while enabling higher penetrations of converter interfaced units such as renewable energy sources to connect to the grid.
Communication-based methods have been attempted previously to help regulate power system frequency, but such solutions are generally dependent on sensing a frequency deviation and reacting to the sensed deviation, which requires a delayed response.
What is needed is a system or method that satisfies one or more of these needs or provides other advantageous features. Other features and advantages will be made apparent from the present specification. The teachings disclosed extend to those embodiments that fall within the scope of the claims, regardless of whether they accomplish one or more of the aforementioned needs.